Penrith coach Ivan Cleary says he expected the Panthers to be rusty after their bid for a third-straight NRL premiership got off to a bad start with a defeat to Brisbane.

The Broncos secured a 13-12 win on Friday at BlueBet Stadium, stunning Penrith a fortnight after they were upset in the World Club Challenge, beaten by St Helens.

The Panthers had a better share of possession and territory but lacked creativity and cohesion with the ball in hand against the Broncos.

Last year, they opened their campaign with an 8-0 record but will now have to bounce back quickly ahead of next week's game with South Sydney.

"It's a disappointing loss," Cleary admitted.

"We haven't been on the money, totally, at the start of each year.

"We had a good one last year, but the next couple of weeks, we weren't great.

"It's a bit of early-season rust, we've got a different dummy half, a short pre-season, all that stuff adds up."

Cleary's new hooker Mitch Kenny toiled in his first game since stepping into the spot vacated by Api Koroisau, but it wasn't until Soni Luke came on that Penrith played with any panache.

"That's certainly something to work with, that's a positive," Cleary said of Luke's impact.

The other big hole created in the off-season was the left edge spot which was occupied by Viliame Kikau.

The big Fijian back-rower was so damaging as a runner and a decoy for Jarome Luai in Penrith's attack.

Luke Garner is the man tasked with taking on Kikau's role and while he battled well, Cleary expects his combination with Luai to be a slow burn.

"It's going to take a while for 'Garns' to get used to how we play and the intensity we want to play at," Cleary said.

"There's definitely some steps there, it's an adjustment for everyone.

"It's round one, we've definitely got some work to do but we haven't lost any friends with our effort."